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Title: Indications of selenium protection against cadmium and lead toxicity in oilseed rape (Brassica napus)

item WU, Z - Anhui Agricultural University
item YIN, X - Suzhou Institute For Advanced Study, Ustc
item LIN, Z - Southern Illinois University
item Banuelos, Gary
item YUAN, L - Suzhou Institute For Advanced Study, Ustc
item LIU, Y - Suzhou Institute For Advanced Study, Ustc
item LI, M - Anhui Agricultural University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/28/2016
Publication Date: 12/15/2016
Citation: Wu, Z., Yin, X., Lin, Z.Q., Banuelos, G.S., Yuan, L., Liu, Y., Li, M. 2016. Indications of selenium protection against cadmium and lead toxicity in oilseed rape (Brassica napus). Frontiers in Plant Science. 7:1875. doi:10.3389/fpls.2016.01875.

Interpretive Summary: Increased cadmium (Cd) and lead (Pb) pollution is of great environmental concern for biological systems, i.e., plants, animals, and humans in many parts of China. In plants, Cd is readily taken up by roots and translocated into the leaves, where it can cause visible symptoms of injury such as chlorosis, growth inhibition, and interfere with many cellular functions. Lead is not easily taken up but its accumulation in the plant can lead to the disintegration of enzymes and structural proteins. Both heavy metals and their respective accumulation in plants threatens the food security in China. Presently, researchers are seeking alternative strategies to reduce heavy metal concentrations in plants. In this regard, selenium (Se) has been used as a potential antagonist to heavy metal absorption in biological systems. For this reason, the role of Se in mitigating environmental stress has been extensively investigated in animals and humans and to a lesser extent in plants. Recent findings have shown that Se in small concentrations can increase the plant's tolerance against oxidative stress. In the present study, the protective effect of Se against accumulated Cd and Pb in rape plants was investigated. The results showed that the addition of Se to growth medium reduced Pb and Cd's peroxidation activity. The protective effect of Se in reducing Cd or Pb toxicity in plants may be attributed to a competition between Se and heavy metals for binding with functional bioligands, as well as the in vivo formation of Cd-Se or Pb-Se insoluble complexes within the plant.

Technical Abstract: Increased cadmium (Cd) and lead (Pb) pollution from industrial, agricultural, energy and municipal sources may have a toxic impact on food chain quality in China. In plants, Cd is readily taken up, while Pb is slowly absorbed. The uptake of both metals interferes with many cellular functions in the plant but their respective intake in the food chain is of greatest concern. As a potential antagonist against metal absorption, selenium (Se) has been shown to minimize toxic effects exerted by heavy metal absorption. In the present study, oilseed rape (Brassica napus) was grown in a soil culture with Pb (added as Pb acetate at 300 or 500 mg/kg) in the presence of Se (added as selenate at 1, 5, 10, 15, 20 mg Se/kg) and with Cd (added as cadmium chloride at 1 or 5 mg/kg) in the presence of Se (added as selenate at 1, 5, 10, 15, 20 mg Se/kg), respectively. Results showed that the additions of Se from 10 to 20 mg/kg reduced both Cd and Pb content by at least 50% from 40 to 100 days of exposure. Selenium at 15 mg/kg reduced the negative effects of Cd and Pb on GSH-Px activity (antioxidative enzyme activity) to the greatest extent. In addition, the addition of Se at 10-15 mg/kg reduced the limitation of lipid peroxides and the production of reactive oxygen species. The present study indicates the pronounced role that Se may both play in protecting rape plants from Cd or Pb toxicity, as well as reducing their respective concentrations in the plant tissue. These observations may be attributed to the competition between Se and Pb and Cd binding with functional proteins and bioligands. Consequently, a soluble complex was respectively formed and reduced the availability of "free" toxic Pb and Cd ions in the plant.